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這是我的logcatNullPointerException異常不對勁pDialog.dismiss（）
12-14 10:46:52.089: D/skia(6391): ---- fAsset->read(2202) returned 0
12-14 10:46:52.119: D/request!(6391): starting
12-14 10:46:52.569: D/Retrieve attempt(6391): {"posts":[[{"position":"user","address":"Bunga Raya","mobilenumber":"0124331292","email":"[email protected]","name":"Jiawei","state":"Melaka","userid":"1","postcode":"75450","password":"123456abcd","cardbalance":"20","city":"Bukit Beruang"}]],"message":"Post Available!","success":1}
12-14 10:46:52.569: D/Retrieve Successful!(6391): res: Post Available!
12-14 10:46:52.569: D/AndroidRuntime(6391): Shutting down VM
12-14 10:46:52.569: W/dalvikvm(6391): threadid=1: thread exiting with uncaught exception (group=0x40018578)
12-14 10:46:52.579: E/AndroidRuntime(6391): FATAL EXCEPTION: main
12-14 10:46:52.579: E/AndroidRuntime(6391): java.lang.NullPointerException
12-14 10:46:52.579: E/AndroidRuntime(6391): at com.pmss.CheckCard$RetrieveUser.onPostExecute(CheckCard.java:158)
12-14 10:46:52.579: E/AndroidRuntime(6391): at com.pmss.CheckCard$RetrieveUser.onPostExecute(CheckCard.java:1)
12-14 10:46:52.579: E/AndroidRuntime(6391): at android.os.AsyncTask.finish(AsyncTask.java:417)
12-14 10:46:52.579: E/AndroidRuntime(6391): at android.os.AsyncTask.access$300(AsyncTask.java:127)
12-14 10:46:52.579: E/AndroidRuntime(6391): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
12-14 10:46:52.579: E/AndroidRuntime(6391): at android.os.Handler.dispatchMessage(Handler.java:99)
12-14 10:46:52.579: E/AndroidRuntime(6391): at android.os.Looper.loop(Looper.java:130)
12-14 10:46:52.579: E/AndroidRuntime(6391): at android.app.ActivityThread.main(ActivityThread.java:3687)
12-14 10:46:52.579: E/AndroidRuntime(6391): at java.lang.reflect.Method.invokeNative(Native Method)
12-14 10:46:52.579: E/AndroidRuntime(6391): at java.lang.reflect.Method.invoke(Method.java:507)
12-14 10:46:52.579: E/AndroidRuntime(6391): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
12-14 10:46:52.579: E/AndroidRuntime(6391): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
12-14 10:46:52.579: E/AndroidRuntime(6391): at dalvik.system.NativeStart.main(Native Method)
行158：pDialog.dismiss();
這是我CheckCardBalance.java
public class CheckCard extends ActionBarActivity {
TextView checkbalance;
private ProgressDialog pDialog;
private JSONArray cardbalance = null;
// JSON parser class
JSONParser jsonParser = new JSONParser();
private static final String USERINFO_URL = "http://192.168.1.10:1234/PMSS/userinfo.php";
// ids
private static final String TAG_SUCCESS = "success";
private static final String TAG_MESSAGE = "message";
private static final String TAG_POSTS = "posts";
private static final String TAG_CARDBALANCE = "cardbalance";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_check_card);
checkbalance = (TextView) findViewById(R.id.checkbalance);
// checkbalance.setKeyListener(null);
//This make the textbox to grey color which means you can do nothing to it
// checkbalance.setEnabled(false);
}
/**
* Set up the {@link android.app.ActionBar}, if the API is available.
*/
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private void setupActionBar() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
getActionBar().setDisplayHomeAsUpEnabled(true);
}
}
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
// loading the comments via AsyncTask
new RetrieveUser().execute();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.check_card, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. Use NavUtils to allow users
// to navigate up one level in the application structure. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
//
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
public class RetrieveUser extends AsyncTask<Void, Void, Boolean> {
int success;
String message;
String CardBalance = null;
@Override
protected void onPreExecute() {
super.onPreExecute();
ProgressDialog pDialog = new ProgressDialog(CheckCard.this);
pDialog.setMessage("Loading...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected Boolean doInBackground(Void... arg0) {
String post_username = "[email protected]";
// SharedPreferences sp = PreferenceManager
// .getDefaultSharedPreferences(CheckCard.this);
// String post_username = sp.getString("username", "anon");
try {
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("email", post_username));
Log.d("request!", "starting");
// getting product details by making HTTP request
JSONObject json = jsonParser.makeHttpRequest(USERINFO_URL, "POST",
params);
Log.d("Retrieve attempt", json.toString());
// I know I said we would check if "Posts were Avail."
// (success==1)
// before we tried to read the individual posts, but I lied...
// mComments will tell us how many "posts" or comments are
// available
success =json.getInt(TAG_SUCCESS);
message= json.getString(TAG_MESSAGE);
cardbalance = json.getJSONArray(TAG_POSTS);
Log.d("Retrieve Successful!", "res: " + message);
JSONArray jr = cardbalance.getJSONArray(0);
JSONObject jb = jr.getJSONObject(0);
CardBalance = jb.getString(TAG_CARDBALANCE);
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
pDialog.dismiss();
Log.d("Card Balance Updated!", message);
checkbalance.setText(CardBalance);
}
}
}
從我知道的是，NullPointerException異常（NPE），但是當我想在checkbalance as in TextView上顯示文本時，我在activity_check_card.xml中聲明瞭空文本顯示。
這裏的問題，當我刪除onPostExecute方法pDialog.dismiss();，沒有更多的錯誤，但我希望對話框自行解散，而不是用戶點擊後退按鈕關閉對話框。
就是這樣，我覺得我宣佈兩次進展pDialog ..一個在我的CheckCard類，另一個onPreExecute方法。謝謝你的幫助 –
是的，所以當你聲明成員變量時，你可以這樣聲明。進度mPDialog。 – venciallee
Progress和ProgressDialog有何不同？如果我聲明進步mPDialog它只適用於該方法？ –